The present invention relates to devices for retaining a plurality of printed circuit boards. More particularly, the invention relates to cabinets intended for the storage of spare or currently unused printed circuit boards.
Apparatus for operatively accommodating printed circuit boards or cards wherein connectors into which the boards are plugged are provided on the apparatus for completing electrical connections with electronic components on the boards are well known. Such apparatus is most commonly configured in the form of open racks or cages which include relatively complex edge receiving guides for accurately guiding the printed circuit boards into engagement with their corresponding electrical connectors and for positively retaining the boards against inadvertent dislodgment without gripping the same too tightly or in a manner susceptible of causing damage to the board or to its electrical circuits or components.
Often, the use of open rack-like cages for operatively accommodating printed circuit boards is dictated by the application--i.e. to assure sufficient ventilation and air circulation about the circuit boards to adequately dissipate heat produced by the electronic components mounted thereon. Of course, open cage-type arrangements of this sort provide little overall structural rigidity and strength of the housing and accordingly afford only minimum physical protection to the often complex and expensive printed circuit boards held therein. However, the use of substantially closed--and consequently more protective--cabinets under operating circumstances or conditions could result in an accumulation within the enclosure of an amount of heat sufficient to damage the components or at least adversely affect the operation of the electronic circuits. Hence, the use of protectively enclosing cabinets for powered or operating circuit boards is generally avoided.
On the other hand, it is often necessary to maintain on hand a relatively large quantity of spare printed circuit boards not currently used but which might subsequently be required for replacement of boards then in operation. In accommodating a readily accessible supply of replacement circuit boards, structures similar to those previously described have often been employed since the same are most easily available. But such structures, designed specifically for operative retention of printed circuit boards, suffer from a variety of defficiencies when utilized for non-operative storage of the circuit boards.
The lack of structural strength inherent in the constructural arrangement of an open rack or cage presents a substantiall drawback in that when relatively large numbers of spare printed circuit boards must be kept accessibly on hand multiple stacking of storage units is preferred so as to most efficiently utilize the storage space available. Stacking of the open cage-like racks might, however, result in damage to the racks and to at least some of the printed circuit boards, and a less efficient use of available space becomes necessary.
Moreover, the relatively complex configuration of the printed circuit board retaining guides, which are arranged to grip the boards against inadvertent dislodgment from engagement with the corresponding electrical connectors, are not designed for the continued or repeated insertion and removal of circuit boards common in a storage environment and, should the edge receiving channels or members become distorted or deformed with repeated use, the same could cause damage to the stored boards. In addition, the printed circuit board retaining guides, being intended for precision gripping and retention, are relatively expensive to fabricate and, as a consequence, the overall structures in which the same are provided are themselves excessively expensive for use in nonoperative storage applications.
Another drawback relates to the storage of printed circuit boards of varying thicknesses. Known devices for operatively or otherwise retaining printed circuit boards do not include provision for enabling storage in the same device of boards of differing thicknesses--at least not without disassembly of the unit and substitution of individual edge-receiving channels as required. Since in the storage of printed circuit boards for replacement purposes there is often a relatively rapid turnover of circuit boards and a consequent variation in the kinds and dimensions of those accommodated, it is preferable to enable the simultaneous accommodation of circuit boards having widely differing thicknesses in a single storage unit while retaining each of the boards in an edge-receiving channel substantially conforming in width to the thickness of the board.
It is, therefore, the desideratum of the present invention to provide a device for storing spare printed circuit boards which overcomes the disadvantages of structures currently utilized. In particular, it is an object of the invention to provide a printed circuit board storage cabinet having sufficient structural strength to enable stacking of multiple units and the ability to simultaneously accommodate printed circuit boards of differing board thicknesses.
It is a further object to provide a printed circuit board storage cabinet which includes provision for facilitated interchange of guide surfaces intended to retain and accommodate printed circuit boards of differing board thicknesses.